1. Field of the Invention
The present invention relates to a magnetic disk drive incorporating a slider including a thin-film magnetic head element and a recording medium that is driven to be rotated.
2. Description of the Related Art
A magnetic disk drive comprises a recording medium that is driven to be rotated and a thin-film magnetic head that writes data on the recording medium and reads data from the recording medium. The thin-film magnetic head incorporated in the magnetic disk drive is typically made up of a slider wherein a thin-film magnetic head element (that may be hereinafter simply called a head element) is provided at a rear end of the slider. The slider slightly flies above the surface of the recording medium by means of an air flow generated by a rotation of the medium.
The areal recording density of magnetic disk drives has dramatically increased. To achieve a further improvement in areal recording density, it is required to reduce the distance between the surface of a recording medium and the head element when the magnetic disk drive is operated. To be specific, the distance between the surface of the recording medium and the head element is recently 8 nm or smaller. A reduction in the distance between the surface of the medium and the head element contributes to improvements in reading output and writing characteristics.
On the other hand, if the distance between the surface of the recording medium and the head element is further reduced, the slider is likely to collide with the medium, and the medium or the head element is likely to be worn or damaged. To prevent such wear or damage of the recording medium and the head element, a lubricating film made of liquid lubricant is provided on the surface of the medium in prior art.
There are two types of start and stop systems of the magnetic disk drive: a contact-start-stop system and a load-unload system. In the contact-start-stop system, when the magnetic disk drive is stopped, that is, the recording medium is stopped, the slider is in contact with the medium. Then, after the magnetic disk drive is started, that is, the medium is started to rotate, the slider is made to fly above the surface of the medium by means of an air flow generated by the rotation of the medium. When the medium is stopped, the slider is brought to contact with the medium again. Japanese Published Patent Application H6-4856 discloses a technique in which the lubricating film provided on the recording medium is made to have different thicknesses between a data region and a region in which the slider performs contact and flying.
In the load-unload system, when the magnetic disk drive is stopped, the slider is made to retreat from the surface of the medium. Then, after the magnetic disk drive is started, the slider is loaded on the surface of the medium. When the magnetic disk drive is stopped, the slider is made to retreat (unloaded) from the surface of the medium. As a type of load-unload system, a ramp load system as disclosed in Japanese Published Patent Application H11-306704, for example, is widely employed. In the ramp load system, a ramp is provided near the recording medium while a tab is provided on a suspension flexibly supporting the slider. The tab gets on the ramp so that the slider leaves the surface of the medium. According to the load-unload system, it is possible to prevent a collision of the slider with the recording medium when the magnetic disk drive is started or stopped. Japanese Published Patent Application 2000-30201 discloses a technique in which the recording medium is rotated at 5000 rpm or greater, and a thickness of the lubricating film in a region where load or unload is performed is made greater when the medium rotates, compared with a thickness thereof when the medium is stopped.
On a surface of the slider that faces toward the recording medium, a protection film for protecting the head element is formed. A diamond-like-carbon film is widely used as the protection film. Japanese Published Patent Application 2001-195717 discloses a magnetic head comprising a protection film made up of a diamond-like-carbon film and a tetrahedral amorphous carbon film formed thereon. Japanese Published Patent Application 2003-226971 discloses a slider comprising a tetrahedral amorphous carbon film containing fluorine therein as a protection film.
As a technique for reducing the distance between the surface of the recording medium and the head element, a technique of dynamically controlling the distance between the surface of the medium and the head element is disclosed in each of U.S. Pat. No. 5,991,113, Japanese Published Patent Application 2003-168274, and Japanese Published Patent Application 2003-272335. According to this technique, a heating element is provided in the slider to cause an expansion of a portion of the slider by heat produced by the heating element to thereby bring the head element closer to the recording medium, and the distance between the surface of the medium and the head element is controlled by controlling the heating value.
As previously described, the distance between the surface of the recording medium and the head element in the magnetic disk drive has been reduced. Furthermore, in the magnetic disk drive, there are some cases in which the coil in the head element produces heat while writing is performed, thereby making the head element protrude to get closer to the medium, and the distance between the surface of the medium and the head element is thereby made smaller than a desired value. In addition, in the magnetic disk drive, there are some cases in which the distance between the surface of the medium and the head element is made smaller than a desired value because of factors such as variations in load applied to the slider by the suspension and variations in orientation of the slider when flying. Moreover, there are also cases in which the distance between the surface of the medium and the head element is made to be of a small value by the control of the distance between the surface of the medium and the head element as disclosed in each of U.S. Pat. No. 5,991,113, Japanese Published Patent Application 2003-168274, and Japanese Published Patent Application 2003-272335. It has been found out that the following problem arises when the distance between the surface of the medium and the head element is reduced because of the foregoing various factors. The problem is that, when this distance is reduced, the lubricating film on the recording medium flows and the thickness of the lubricating film varies even though the slider does not touch the medium, and, furthermore, the lubricating film and the slider resonate to cause vibrations of the slider. If the slider is thus vibrated, the distance between the head element and a magnetic layer of the recording medium varies and the error rate increases. It is difficult to reduce the distance between the surface of the medium and the head element while preventing vibrations of the slider due to the resonance of the lubricating film and the slider as mentioned above through the use of any of the techniques disclosed in Japanese Published Patent Application H6-4856, Japanese Published Patent Application H11-306704, Japanese Published Patent Application 2000-30201, Japanese Published Patent Application 2001-195717, Japanese Published Patent Application 2003-226971, U.S. Pat. No. 5,991,113, Japanese Published Patent Application 2003-168274, and Japanese Published Patent Application 2003-272335.